90s Connecticut Guy
My college roommate was from a pretty dominant program in Connecticut in the 90s, Xavier HS.
They were no FM for sure, but there are definitely similarities. One of them was that all of these All State and All New England kids were pretty mediocre in college, and this included my roommate.
His perspective, and one that I agree with, was that kids that would have been 4:45 milers in most programs ran 4:25 in Xavier's. When it came to XC, it was bigger than the individual and they knew if you they were toeing the line at the state meet they had a certain expectation and they were going to compete well. Similarly, other runners looked at the black singlets with an X in awe and fear.
But why did these guys run poorly in college? 1.) Because they were average HS talents who greatly overachieved. 2.) Because college programs are more about the individual and there isn't a dominant coach forcing them to do all of the little things that made them overachieve in HS. 3.) Average talents don't make it at that level.